1. Field of the Invention
The present invention relates generally to automated inspection systems for cylindrical carbon articles, especially graphite electrodes.
2. Description of the Prior Art
The current technology in the manufacture of steel from recycled scrap steel materials is highly dependent upon the use of electric arc furnaces wherein the steel scrap and other material is melted by a high energy electric arc. One critical component utilized in an electric arc furnace is a column of large carbon electrodes. These carbon electrodes are generally cylindrical in shape with integral threaded pin and box connections on either end. The cylindrical carbon electrodes typically have diameters in the range of 15 to 30 inches, and typically have lengths ranging up to about ten feet.
The carbon electrodes are used up during the steel making process in an electric arc furnace. Essentially, the end of the electrode burns away during the steel making process. The electrodes are placed in the furnace as a threaded column of electrodes, and as the lowermost electrode burns away the column of electrodes is advanced and periodically a new electrode segment is added to the top end of the column.
In addition to the expected burning away at the lower end of the electrode, due to the extreme environmental conditions within the steel making furnace, the electrodes sometimes suffer a more rapid and undesired consumption rate due to physical non-conformities in the electrode. Examples are cracks and the like, which may cause chunks of the electrode to separate, thus increasing the rate of usage of the electrode and decreasing the life of the electrode and its effectiveness.
There is, therefore, a need for a quality control technique to provide nondestructive testing of electrodes to identify internal defects which are not otherwise observable. Such systems can be utilized as a monitor on the manufacturing process to improve the various process parameters, thus resulting in an improved work product as a batch of carbon electrodes is manufactured. Such an inspection system can also be utilized to detect and eliminate unsatisfactory product prior to delivery to the customer who will use the same in an electric arc furnace. In addition, the system can be used to correlate internal electrode structures with manufacturing process parameters and product performance to identify superior process parameters.
A predecessor of the present invention has been utilized, which is a much more rudimentary system for testing of the type just described. The predecessor system provided a cradle for receiving the carbon electrode to be tested. The carbon electrode was moved onto the cradle by movement in a transverse direction perpendicular to the length of the carbon electrode. A single pair of roller transducers was then positioned on opposite sides of the electrode through the use of two separate transducer placement mechanisms. During the testing operation, the roller transducers were each simultaneously moved along the entire length of the electrode to be tested. The roller transducers generated an axial topographic scan image of the electrode. The roller transducers were then disengaged and removed from the carbon electrode, which was picked up from the cradle and again moved in a direction transverse to the length of the electrode to remove it from the test cradle.
While the predecessor system was operable to perform the general type of inspection which is the subject of the system of the present invention, it was not capable of operating at sufficient capacity to provide the volume of testing desired.
Accordingly, there is a need for an improved testing system of the type generally described providing improved systems for handling of the electrodes in order to allow testing of a high volume of carbon electrodes, such as would be manufactured by a modern electrode manufacturing plant.